We have the rings:green (courage, allegedly) -- the sin, prideyellow (fear) -- the sin is most likely gluttony. They feed on other people.blue (hope) then becomes Envy, which kind of fits because they only work by being around green rings, as if they were envious of their power.orange (greed) -- this is easy, greed.red (anger) -- Also easy, wrathpurple (love/lust) -- Lust, of courseviolet (compassion) -- given the degree to which they didn't do a damn thing when they had the chance to, "sloth" is the obvious answer.

The black and white rings don't fall into this category, but then, I had to shoehorn things a bit too.